dictyBase is a new model organism database whose development began in July 2002. The goal of dictyBase is to use the recently completed sequence of the Dictyostelium genome to organize biological knowledge derived using Dictyostelium as an experimental system. dictyBase was largely built using the database schema and code from existing model organism databases and the Generic Model Organism Database project (GMOD). It was officially launched in July 2003 and has been accessed over 600,000 times by more than 100,000 individual IP addresses. It has become an indispensable resource for investigators using Dictyostelium or seeking to use its complement of genes in comparative genomics studies. During the first funding cycle manual curation of the Dictyostelium genome improved the gene models produced by the automated sequence analysis pipeline in approximately 18% of the genes that were reviewed. Specific aims for this application are to continue the manual curation effort, to provide expert support to dictyBase users, to provide resources that facilitate research using Dictyostelium, to expand the types of data available through the database, to establish links to databases holding other Dictyostelium data, and to begin to develop the infrastructure to hold and curate the genome sequences of other amoebae. Because of its location in the evolutionary history, detailed curation of Dictyostelium genes and experimental results will give insights into the function and evolution of many genes and biological process important for fundamental understanding of biology important for human health. Examples of this include identifying genes required for growth of intracellular parasites, characterizing the mechanisms responsible for cell migration that will increase our understanding of wound healing, generation of immune responses and tumor metastasis and the identification of genes responsible for response to drugs such as antidepressants and cancer chemotherapeutics. As the number of genomes being sequenced increases, analysis of these new genomes is heavily dependent on the body of knowledge resulting from a few well characterized and carefully annotated genomes. dictyBase provides a unique complement to existing genome databases because of the body of knowledge available for Dictyostelium, its position in the evolutionary tree, the research tools available and the strength of ongoing Dictyostelium research.